Steam engine valve mechanism



Jan. 8, 1946. c. R. BRIGGS STEAM ENGINE VALVE MECHANISM 2 Sheets-Sheet 1 Filed Jan. 6, 1944 lA/VENTOP CARL P, 5/?!665. by 174 M 414 Jan. 8, 1946. c. R. BRIGGS 2,392,350

STEAM ENGINE VALVE MECHANISM Filed Jan. 6, 1944 2 Sheets-Sheet 2 Ill.| 1i

f -Z 33 ZjZ 32 j g j "BY A TTOIPNEKS C/ML R. Belqas.

Patented Jan. 8, 1946 UNITED STATES A E .L- FFICEfE STEAM ENGINE VALVE lVIECHANISM Carl R. Briggs, Mantua, Ohio Application January 6, 1944, SerialNo. 517,215 '3- Claims. (01. V

' 'ance spaces l9 at the ends of the engine cham This invention relates to steamengine valve mechanism; and mor particularly to piston valve mechanism. v One object of the invention is to provide improved piston valve mechanism so arranged as to permit the enginefto become self-scavenging as to any water which might collect beyond clearance volume and by its incompressjibility interfere with engine operation or reduce affording relief for condensate otherwise trapped during compression.

Still another object is to provide improved piston valve mechanism of relatively simple but highly eificient form, capable of convenient manufacture, assembly and adjustment, and which'will not get out of order in service.

Further objects of the invention in part are obvious and in part will appear more in detail hereinafter,

In the drawings, which represent one suitable embodiment of the invention,

Fig. 1 is a central longitudinal section through the engine and its valve mechanism;

Fig. 2 is a, detail view, on a larger scale, corresponding to Fig. 1 and showing one of the piston valves, with the parts separated for clarity of illustration;

Figs. 3 and 4 are respectively end and side elevations of one of the piston rings;

g s. 5 and 6 are similar views of another ring; an

Figs. 7 and 8 are similarviews of still another ring.

Referring to the drawings, the steam engine to be driven is shown more or less conventionally. While the invention may be applied to single acting engines, it is shown applied to a double acting engine including a cylinder H! in the chamber ll of which travels the reciprocating piston l2 carried by a piston rod l3. The crosshead, connecting rod, crankshaft and valve operating gear require no illustration because they may be of conventional forms and form no part of the invention.

The valve mechanism is housed within a valve casing l4 attached to or ,forming a. part of the her I I.

Within the valve chamber are located two like piston valves, marked generally 20, mounted in spaced relation on a valve rod 2| guided at 22in one end of the valve casing and at the other end extending out through a suitable stuffing 'box '23 able on the rod and adjustable by a. nut 21 capable of being looked, a castellated nut and a cotter pin 28 being shown for the purpose. Heads 24, 25 ar provided with telescoping sleeves 29, 30

and are normally urged apart by a spring 3 I. In

the cavity or space 36' between them are mounted suitable sealing piston rings outwardly eXpahsible against the wall of the valve chamber, or the lining sleeves 40 inserted therein. Any suitable arrangement of rings may be employed. The drawings show four narrow outer split rings 32, lying side by side, all engaging the chamber wall. Within them are two wider split rings sleeved one upon the other, to-wit, an outer ring 33 and an inner ring 34. Nuts 21 are adjusted to move the heads 24, 26 together until, with the parts assembled and in operative position, the rings closely fit each other but are movable readily. On each piston valve that head 24 or 26 which is presented to the live steam space (head 26 in the form shown) is provided with a small port or opening 35 supplying full steam pressure to cavity 36 within the piston.

The operation is as follows: i In Fig. 1 the parts are shown in the positions they occupy shortly after the admission point.

Steam is entering the engine cylinder through the port l8, and on the opposite side of thepiston is moving to exhaust through the port lBa. The engine piston ha passed the dead center point and is moving toward the right. The operation of the left-hand piston valve will be described, it being understood that the right-hand valve operates in the same manner.

When some 20 to 30 per cent or more of the stroke has been completed, the valve moves to the left and closes port 18 at the cut-oif point. During the remainder of the stroke the steam expands adiabatically to the accompaniment of decreasing pressure. Near the end of the stroke the valve again opens the port, connecting the cylinder chamber with exhaust, at the release the I point. The englne'chamber remains connected with exhaust during the return stroke of the piston until approximately /3 of the return stroke has been completed, when the valve again closes port 3, and the remaining steam is trapped in the cylinder and compressed.

It is during this compression stage, and slightly before the'engine piston reaches the dead center point, that the piston valve of this invention permits evacuation torzscavenging of' -water' of "condensation which'may'h'ave lodged'orcollected in the engine cylinder ahead of the piston. Not only is the water crowded into the clearance space by the adiabatic expansionzofthe steam-in the working end of the engine chamber, but the engine piston is also subject to the=efiect=of-the flywheel. As previously stated, with .the .various moving parts in the position shown in Fig. 1, the engine piston I2 has passed dead centeratthe leftendofitsstroke and ismoving to the right. The valve piston'2fl at the right of Fig. '1 is slowly .moving to the'left and.is,just.beginni ng to close .port -I'8 a.. Obviously, .the pathof travelof valve ,pistonlfl isconsiderably'shorter thanthat o'fenagine piston 1.2. and consequeritlyits rate of .move- .:ment isslower. By the time, piston l2'haspasse'd .thehalf way markin .its pathcf travel, andis approaching right dead center, valve ,piston T211 ;has just closed sport 18a, and piston f2 rbegins'to build up backpressure inthe right .end of theeng gine cylinder. I

W -:At-:this =pointthe situation with respectto v.pis- .ton -2ll:m ay be briefiyhoted. v.By reason of the aperture 35 inmovable end head 2'S,.the steam pressure, within .piston 20 is equal .to the pres- 35 :;sure .of the steam from they supplysource. Were :this not. so, the outersteam .pressure on head .25 would move it to bind rings-32,33,3 1 and reduce their .mobility practically-to -zero, impairing their sealing .eificiency. Equalization-of pressure .on -the inner and outer surfaces of head 26 leavesit .under @c'ontrol .of spring 3 l as restrained by nut -21, -;and leaves :rings 32 free .from bindingside pressure :against -1B3.Gh:.0thl", so that they are PfTBG to :flexinwardlyif pressure on their .quter periphery builds up so :as to overcome :in-ternal .-steam; pressure. v v p Returning -to piston |2 :which is ;building up aback pressure in approaching rightdead-:center, if this accumulated back pressure passes the rcritical ftbalan'ce value, and exceeds the ;pressure ".within ;piston .23, :any one {or tmore-of rings 352 which happen 'to be above port 4.8a :are 'forced "upwardly, carrying rings 33 --and 34 :before :them. Relief of back pressure -.to -.thelo-wer interior portion of piston 20 is therebypermitted, andsuch "aexcess pressure; is further relieved towards :the

.zleftrbetween rings 33 and r35 and-around the low- :errper'ipheral edge of :fi-xed ahead '24 which :isaof reduced peripheralextent,..into the exhaust portion-of the .p'istonavalvachamber.

, ZBy the time the piston 42 has moved-to right dead center, where maximum back pressure is normally incurred with previously -known *con- .structi'ons, destructive, 2 or injurious pressure has been relieved in:the presentconstructiom-anwen- -:gine efficiency isgreatly enhanced.

The -.operation of the disclosed structure has been detailed with reference to fluid pressure -f any kind, :and :is obviously the --same; whether .-the back pressure :is developed 'by residual -steam .or by .condensedjliquid. -In either case the result ianrodueed; is identical.

:fllhe mechanism rot -relief past-the rin s wil wary somewhat depending on valve timing, and

10 of rings 32 is raised, :rings 33 and-=34 are necessarily raised thereby. It"will be understood of course that the situation is in a state of continual "change, since pistons are always moving when atheyzregister'with apertures l8 and l8a.

Of course, apart from the matter of scavenging of "water of condensation, and considering the pistonvalves only from a standpoint of their control of admission and exhaust of steam, said piston' valves permit no escape of live steam to ex- 20 -haust because the pistons are adjusted so that theurings are in'close contact .with .each other and with the piston heads, and the rings arehel'dout- 'wardly by their .ownexpansion against the wall of the valve chamber, so' that, all leakage is avoided or prevented.

"The .construction is'quite simple, is capable of .covenientassembly, setting up and adjustment, and is durable and 'eificien't in operation; 'Other advantages ofthe invention will" be apparentto those skilled in theart.

'What}I claim is:

'1. Engine "valve 'mechariism lof "the'char'a'cter described, comprising a' valve housin'g'havingfa cylindrical chamber .provided with steam supply, .engine. and exhaust ports, anda reciprocatingjrod carrying .a valveslidablein .said chamber and cooperating with said .ports, said valve "ingeneral'being of piston form and'inclu'ding relative- .ly adjustable spaced disc-formheads on saidlrdd forming a .cavitylbetweenthem, spring meansoperatively engaging the opposed innersur'faces o'f saidzadjustable heads, and resiliently Zurgingsa'id heads apart, means providing communication from the steam supplyto said cavity, and a'rejsil- 'ie'nt expansiblepis'ton ring exposedto-thejpffessure in said cavity and sensitive to abnormalrri's'e -.or pressureiinithe engine clearance'spa'c'e and "thereby adapted during compression :to permit 5 escapeto exhaust of condensatetrapp'ed inrsai'd space. "2.Engine 'valve mechanism of the character described, comprising a .valve "housing having a cylindrical chamber provided'yvi'th 'steam"supply, engine and exhaust ports, and .a reciprocating rod 'carryinga valve slidable insaid'cliamberjand cooperating with saidports said'valve in general being of piston form and including a "stationary 'headffixedinposition .withrespect to said rod,"a movable .head, "slidable' along "said rod, adj us'table -stop"me'ans for limiting, slidable movementpf .said'movable head along said ro d, resilientb'iasfing means disposed "betweenand in *contacfiwith both saidheads to normally maintain a'fmaximum spacing between 'said "heads 'but "to-permit said movable head toyield towards 55am stationary "head said spacing-between said heads "constitutingacavity therebetween, means providing a communication ?'from the steam supply to said cavity,'an'd a resilientexpansible'and compressible ;piston tringex'posed t'o the :pressure insaid cavity and sensitive to abnormal rise -of=pressure in, Zthe, engine fcl'earance "space, and thereby adaptedduring compression to {permit escapeEto exhaust,'o'f condensatetrappedin said space.

3. Engine valve mechanism of the character described, comprising a valve housing having a cylindrical chamber provided with steam supply, engine and exhaust ports, and a reciprocating rod carrying a valve slidable in said chamber and cooperating with said ports, said valve in general being of piston form and including a stationary head fixed in position with respect to said rod, a movable head, slidable along said rod, adjustable stop means for limiting slidable movement of said movable head along said rod, resilient biasing means disposed between and in contact with both said heads to normally maintain a maximum spacing between said heads but to permit said movable head to yield towards said stationary head, said spacing between said heads constituting a cavity therebetween, means providing a communication from the steam supply to said cavity, a plurality of sealing rings disposed side by side in said cavity, and radially outwardly expansible against said valve housing, a lining sleeve within said sealing rings and likewise radially outwardly expansible against said sealing rings, said sealing rings and lining sleeve being also inwardly compressible, and being exposed to the pressure in said cavity and sensitive to abnormal rise of pressure in the engine clearance space, and thereby adapted during compression to permit escape to exhaust, of condensate trapped in said space.

CARL R. BRIGGS. 

